EDB — 20F

[20F] Let $I\subset ℝ$, $x_0\in \overline{ℝ}$ accumulation point of $I$, $f:I\to ℝ$ function. We define

where the first ”inf” (resp. the ”sup”) is performed with respect to the family of all the deleted neighbourhoods $U$ of $x_0$; and the neighbourhoods will be right or left neighbourhoods if the limit is from right or left.